The field of art to which the invention relates comprises meters for measurement of fluid flow volume and having a sensing probe for effecting temperature correction of fluid volume at temperatures deviating from a standard temperature for the metered fluid.
In fluid meters of the type commonly utilized for the volumetric measurement of gaseous fluids, such as gas meters, density of the gas and hence its heating value per unit of volume varies with changes of gas temperature. Consequently, the volume of gas passing through the meter, as recorded on an indicator driven by the meter, does not actually indicate what the volume would measure at a standard temperature used for computing the cost of gas consumed. Variations in gas density due to temperature changes thus result in under-registration of the meter at low temperatures and over-registration at high temperatures. It is therefore necessary, particularly in the case of a large gas-using installation to provide means to compensate for the effect of temperature variation.
A mechanism for temperature correction of metered fluid is disclosed for example in U.S. Pat. No. 3,581,566 incorporated herein by reference. Disclosed therein is a mechanical compensating device which automatically compensates for temperature deviations via a volume correction mechanism that controls the drive of a compensated register. By compensating in this manner, the volumetric displacement of the meter is automatically corrected for variations in gas temperature from a standard based temperature so as to establish an accurate measurement for the consumer.
Such mechanisms as disclosed in the aforementioned ""566 patent includes an elongated temperature probe of a wound bimetallic construction. The probe is emerged in the fluid flow and senses fluid temperature passing through the meter. In response to temperature changes, the probe serves to mechanically vary the counter index for correcting the volume readout to a predetermined standard or base temperature.
The probe, in this arrangement, is supported within the meter extending cantilevered into the flow path of the passing fluid. At such time as the probe needs to be serviced or replaced, it is customary to withdraw the probe from its meter support and service or replace it as required. Yet because the probe, is of a wound elongated fragile construction and cantilevered over a substantial portion of its length, handling can prove difficult to avoid injury during repair or replacement that could impair its operational accuracy. At the same time, the distal end of the cantilevered probe being unsupported has a tendency to droop whereby a rubbing contact can be incurred that likewise can adversely affect its operational accuracy.
Despite recognition of the foregoing, a ready solution for safeguarding the probe during repair or replacement has not heretofore been known.
It is therefore an object of the invention to provide apparatus for protecting the probe unit of temperature correction apparatus for a fluid meter against injury when handled.
It is a further object of the invention to utilize a structure that largely encloses and supports the probe against injury at least when serviced, manufactured, shipment, assembly, testing, retrofit, etc.
It is a still further object of the invention to effect the previous objects with a structure that is substantially uncostly to fabricate and relatively easy to assemble about the probe.
The invention relates to a protective article for a corrective temperature probe of a fluid flow meter. More specifically, the invention relates to a novel construction of such an article that can protect the fragile probe against injury during handling of the probe in situations that could otherwise result in damage producing operational inaccuracies for effecting temperature correction within the meter.
The foregoing is achieved in accordance with the invention utilizing a tubular metal sheath closely surrounding the injury prone probe. The sheath is preferably of a weldable metal composition, such as stainless steel, that closely surrounds the probe and is secured at its ends within the meter. The sheath is internally sized to permit arcuate displacement of the bimetallic sensing elements in response to temperature changes to which is exposed along its length. Preferably, the sheath includes a plurality of open slots through which a cross flow of fluid within the meter can contact the sensing element for permitting temperature changes to be encountered. When connected as to an operative reset mechanism of the meter, correction reset occurs continuously on an ongoing basis. Yet by virtue of the surrounding sheath, handling injuries such as has occurred in the past is eliminated so as to benefit from a substantially increased life expectancy and continuing accuracy of the probe unit.